Genetic Aspects of Keratoconus: A Literature Review Exploring Potential Genetic Contributions and Possible Genetic Relationships with Comorbidities.

INTRODUCTION: Keratoconus (KC) is a complex, genetically heterogeneous, multifactorial degenerative disorder that is accompanied by corneal ectasia which usually progresses asymmetrically. With an incidence of approximately 1 per 2000 and 2 cases per 100,000 population presenting annually, KC follows an autosomal recessive or dominant pattern of inheritance and is, apparently, associated with genes that interact with environmental, genetic, and/or other factors. This is an important consideration in refractive surgery in the case of familial KC, given the association of KC with other genetic disorders and the imbalance between dizygotic twins. The present review attempts to identify the genetic loci contributing to the different KC clinical presentations and relate them to the common genetically determined comorbidities associated with KC. METHODS: The PubMed, MEDLINE, Google Scholar, and GeneCards databases were screened for KC-related articles published in English between January 2006 and November 2017. Keyword combinations of "keratoconus," "risk factor(s)," "genetics," "genes," "genetic association(s)," and "cornea" were used. In total, 217 articles were retrieved and analyzed, with greater weight placed on the more recent literature. Further bibliographic research based on the 217 articles revealed another 124 relevant articles that were included in this review. Using the reviewed literature, an attempt was made to correlate genes and genetic risk factors with KC characteristics and genetically related comorbidities associated with KC based on genome-wide association studies, family-based linkage analysis, and candidate-gene approaches. RESULTS: An association matrix between known KC-related genes and KC symptoms and/or clinical signs together with an association matrix between identified KC genes and genetically related KC comorbidities/syndromes were constructed. CONCLUSION: Twenty-four genes were identified as potential contributors to KC and 49 KC-related comorbidities/syndromes were found. More than 85% of the known KC-related genes are involved in glaucoma, Down syndrome, connective tissue disorders, endothelial dystrophy, posterior polymorphous corneal dystrophy, and cataract.

Effect of Conus Eccentricity on Visual Outcomes After Intracorneal Ring Segments Implantation in Keratoconus.

PURPOSE: To investigate the potential impact of cone eccentricity on visual outcomes after Keraring (Mediphacos, Belo Horizonte, Brazil) implantation for keratoconus. METHODS: Nineteen eyes from 19 patients with keratoconus who underwent femtosecond laser-assisted Keraring implantation for keratoconus were included in this retrospective study. Uncorrected visual acuity (UDVA), corrected visual acuity (CDVA), keratometric readings, central corneal thickness, maximum keratometric distance from corneal apex (DKmax), corneal thinnest point from corneal apex (DTh), and coma were evaluated preoperatively and 6 months after the Keraring implantation. DKmax and DTh were used as metrics reflecting the eccentricity of the cone. RESULTS: UDVA, CDVA, keratometric readings, and coma improved at 6 months postoperatively. However, there was no correlation between DKmax or DTh and visual outcomes at 6 months postoperatively. CONCLUSIONS: The data did not show any impact of the cone eccentricity on visual outcomes after Keraring implantation for keratoconus at 6 months postoperatively. [J Refract Surg. 2018;34(3):196-200.].

Full-thickness macular hole associated with congenital simple hamartoma of retinal pigment epithelium (CSHRPE).

PURPOSE: To report a unique case of congenital simple hamartoma of retinal pigment epithelium (CSHRPE) associated with full-thickness macular hole (FTMH). METHODS: A 14-year-old female with a previous diagnosis of simple hamartoma of retinal pigment epithelium in the left eye presented with a 3-week onset of reduced visual acuity in the same eye. Complete ophthalmological examination with spectral domain ocular coherence tomography (SD-OCT) and autofluorescence imaging was carried out. Results were compared with the last 4-year follow-up data. RESULTS: On examination, visual acuity in the left eye was counting fingers compared to 20/100 documented in the last follow-up. Fundoscopy revealed a nodular, heavily pigmented, circumscribed foveal mass, with 0.5 mm basal diameter and 1.1 mm thickness corresponding to the simple RPE hamartoma. Although the latter remained unchanged throughout the follow-up period, a new lesion at the inferior edge of the hamartoma was noted. SD-OCT confirmed the presence of a FTMH with no evidence of associated epiretinal membrane, vitreomacular traction or posterior vitreous detachment. After explaining the risks and benefits of vitrectomy for FTMH, the patient declined surgery. CONCLUSIONS: CSHRPE may have associated features such as feeding vessels, retinal surface wrinkling, pigmented vitreous cells, retinal exudation and vitreoretinal adhesion. The case presented herein broadens the clinical spectrum of CSHRPE and emphasizes that despite the benign nature of the lesion, which remains stable without growth, visual loss may occur, attributable to foveal traction and development of FTMH. We postulate that protrusion of the tumor into the vitreous cavity results in tissue stretching and development of anteroposterior and tangential forces which may lead to development of macular hole.

A serious refractive multifocal intraocular lens complication in Meniere's disease.

PURPOSE: To report an unfortunate case of patient selection for multifocal intraocular lens (MIOL) implantation. METHODS: Interventional case report. RESULTS: A 69-year-old woman with bilateral corticonuclear cataract underwent uneventful phacoemulsification with diffractive MIOL implantation within 1 week. She reported no previous medical history. A few days later she had persisting dizziness and experienced extreme photic phenomena, which progressively deteriorated. After intensive conversation, we discovered that our patient had a medical history of Meniere's disease. Bilateral intraocular lens exchange surgery was performed. One week after monofocal intraocular lens implantation, the patient was satisfied with the final visual outcome and did not report any visual complaints. CONCLUSIONS: Retinocortical processing of visual information is impaired in patients with peripheral vestibular disorders such as Meniere's disease. Therefore, these patients are probably not good candidates for MIOL implantation, which requires an intact sensory system with rigorous visuovestibular interaction.